From new longer-acting drugs to promising gene therapy trials, much is changing in the treatment of hemophilia, the inherited bleeding disorder in which the blood does not clot. Hemophilia Awareness Month comes at a time of both progress and remaining challenges.
1. Many more treatment products are being introduced, including some that last longer.
People with hemophilia lack or have defects in a “factor”—a blood protein that helps normal clots form. Of the approximately 20,000 people with hemophilia in the U.S., about 80 percent have hemophilia A, caused by an abnormally low level of factor VIII, and most of the rest have hemophilia B, caused by abnormally low levels of factor IX. Many patients with severe hemophilia give themselves prophylactic IV infusions of the missing factor to prevent bleeding (which otherwise can lead to crippling joint disease when blood seeps into the joint and enzymes released from blood cells erode the cartilage).
Hemophilia factors traditionally have such a short half-life that we tend to treat patients every other day with factor VIII and twice a week with factor IX. The first two longer-lasting products came onto the market within the past year, and more are on the way. So now, with factor IX, it is possible to get an infusion just once a week and not bleed. This is really changing how we think about the disease. So far, the longer-acting factor VIII products are not yet long-lasting enough to make as dramatic a difference in the frequency of infusions. And creating really long-acting factors remains a challenge. …
Today we bring more good news: Following a successful Phase III trial, rFIXFc recently received the green light for marketing from the FDA and from Health Canada.
Developed by Biogen Idec under the trade name Alprolix™, rFIXFc—a modified version of clotting factor IX—is the fruition of a technology first envisioned by three researchers—gastroenterologists Wayne Lencer, MD, of Boston Children’s Hospital, and Richard Blumberg, MD, of Brigham and Women’s Hospital, and immunologist Neil Simister, DPhil, of Brandeis University—for large protein drugs. Their idea: to extend the drugs’ half-lives by protecting them from being ground up by cells. …
Getting drugs to stay in the bloodstream longer is a big deal when it comes to treating chronic diseases. You see, a drug’s half-life—the time it takes for half of a given dose to be cleared from the body—determines how long its effect(s) last.
If a drug’s half-life is short—meaning it’s cleared quickly—patients will have to take the drug frequently. Given that someone with a chronic condition could be on the medication for many years—say, patients with severe hemophilia, who endure frequent infusions of clotting factors—a short half-life can translate into high cost. Depending on side effects and how the drug is administered, quality of life may also suffer.